(1) Field of the Invention
This invention relates to an object lens actuator which drives an object lens in a focusing direction or a tracking direction to position the focal point of the object lens to a target track on the recording surface of an optical disc for the purpose of reading/writing information from/to the recording surface of the optical disc.
(2) Description of the Related Art
For a higher data transfer rate, a disc drive which writes information to a disc-shaped information recording medium or reads information written on the medium is designed to rotate an optical disc at higher speed. For this purpose, the disc drive is mounted with an objective lens actuator which drives an objective lens in a focusing direction or a tracking direction to allow the focal point of the object lens to follow the track of the disc for the accurate writing/reading of information.
A typical object lens actuator includes a magnetic circuit including a yoke and permanent magnets, an object lens, a focusing coil, a tracking coil, a lens holder including them, and a linear support member which has one end fixed to the outer edge of the lens holder and the other end fixed to a stationary element. Of them, the object lens, the lens holder, the focusing coil and the tracking coil form a moving part which is supported movably relative to the stationary element by the support member.
The object lens actuator further includes a stopper member which makes contact with part of the moving part to limit the amount of travel of the moving part toward the disc in order to prevent the moving part to move excessively toward the disc and come into collision with the disc when the moving part is driven in the focusing direction.
In the process of assembling such an object lens actuator, during the soldering step, a solder flux oozes or flies, so that the solder adheres to the surface of a component. In particular, if the solder adheres to the stopper member or the contact surface of the moving part with the stopper member, the moving part and the stopper member may possibly stick to each other when the moving part moves excessively toward the disc to come into contact with the stopper member, which implies an impossibility of controlling the focal point of the object lens.
To solve this problem, an object lens actuator is known from, for example, JP-A No. 10-222858 (claim 1, FIG. 1), in which a protective film is applied to the stopper member in an initial step of the assembling process and then peeled away from the stopper member in the final step so that a solder flux or an adhesive is prevented from adhering to the stopper member in order to prevent the moving part from sticking to the stopper member.